Apparatus for obtaining a controlled rectilinear movement of a rotatably driven actuator member

ABSTRACT

The actuator member of the apparatus is supported for axial movement relative to a reversible rotatable drive member and is locked against rotational movement relative to the drive member. A centrifugally actuated clutch unit on the drive member has separable half nut sections, which when the drive member is rotated, are movable together to form a split nut for engaging a screw section on the actuator member. On axial movement of the actuator member in either direction the split nut overruns the screw section, but is yieldably held in an abutting relation with the screw section for threaded engagement therewith on a reversed rotation of the drive member. When the drive member is stationary and the split nut disengaged from the screw section, the actuator member is yieldably supported for manual movement axially of the drive member through a predetermined distance to maintain at least one end of the screw section in a position to engage the split nut on rotation of the drive member.

United States Patent 1 Kibler 1451 June 5,1973

[75] Inventor: Willis L. Kibler, Detroit, Mich.

[73] Assignee: McCord Mich.

[22] Filed: Apr. 20, 1971 [21] App]. No.: 113,222

Related U.S. Application Data [63] Continuation of Ser. No. 887,168,Dec. 22, 1969,

Corporation, Detroit,

abandoned.

[52] U.S. Cl. ..74/89.15, 74/424.8 A, 192/105 C [51] Int. Cl ..Fl6h27/02 [58] Field of Search ..74/89.15, 424.8 A, 74/105 CS, 105 C, 103 A,89 R; 192/105 C; 137/49, 53

[56] References Cited UNITED STATES PATENTS 2,346,728 4/1944 Carlson..74/424.8 A 1,122,206 12/1914 Jennings ....l92/l05 CS 1,710,694 4/1929Ferenci ..192/103 A 2,694,320 11/1954 Kron ..192/105 C 3,162,073 12/1964Farekas .....74/424.8 A

1,136,940 4/1915 Craft ..137/49 1,268,264 6/1918 Murray ..74/424.81,509,683 9/1924 Miller .;192/105 5 as 54 3 74 66 7Z 1 67 73 I a 2 4 948 i I as l 5 2; i 2 55 g I ---4/ 15 i 41 s 4s 39 Z 53 5 as 2,491,54312/1949 Alfonso ..74/424.8

FOREIGN PATENTS OR APPLICATIONS 661,917 3/1929 France ..192/105 CSPrimary ExaminerCharles J Myhre Assistant Examiner-Wesley S. Ratliff,Jr. AttorneyMcGlynn, Reising, Milton & Ethington [57] ABSTRACT Theactuator member of the apparatus is supported for axial movementrelative to a reversible rotatable drive member and is locked againstrotational movement relative to the drive member. A centrifugallyactuated clutch unit on the drive member has separable half nutsections, which when the drive member is rotated, are movable togetherto form a split nut for engaging a screw section on the actuator member.On axial movement of the actuator member in either direction the splitnut overruns the screw section, but is yieldably held in an abuttingrelation with the screw section for threaded engagement therewith on areversed rotation of the drive member. When the drive member isstationary and the split nut disengaged from the screw section, theactuator member is yieldably supported for manual movement axially ofthe drive member through a predetermined distance to maintain at leastone end of the screw section in a position to engage the split nut onrotation of the drive member.

10 Claims, 10 Drawing Figures APPARATUS FOR OBTAINING A CONTROLLEDRECTILINEAR MOVEMENT OF A ROTATABLY DRIVEN ACTUATOR MEMBER Thisapplication is a continuation of application Ser. No. 887,168, filedDec. 22, 1969, now abandoned.

SUMMARY OF THE INVENTION The apparatus of this invention is compact,economical and capable of being readily installed within limited spacerequirements, such as a vehicle door, to actuate a door lock. Therectilinearly movable actuator member has a reciprocal movementcontrolled through a predetermined distance, and within such distance itcan be electrically reciprocated or manually reciprocated; or it can beelectrically moved in one direction and manually moved in an oppositedirection. A driven connection of the actuator member is automaticallyand positivelymade in response to the operation of its reversibledriving member, and the actuator member is released for a manualoperation whenever the operation of the driving member is discontinued.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspectiveview of an automobile body showing the apparatus of this invention inassembly relation with a door lock latching mechanism;

FIG. 2 is a fragmentary perspective view of a portion of the assembly inFIG. 1 showing the connection of the apparatus with the garnish buttonof the door latching mechanism;

FIG. 3 is an enlarged side view of the apparatus;

FIG. 4 is a longitudinal sectional view taken along the line 4 4 of FIG.3 showing the actuator member of the apparatus in an innermost movedposition;

FIG. 5 is illustrated similarly to FIG. 4 and shows the actuator memberin an outermost moved position;

FIG. 6 is an exploded perspective view of a centrifugally actuatedclutch unit that forms part of the apparatus;

FIG. 7 is a sideelevational view of the clutch unit shown in FIG. 6;

FIG. 8 is an enlarged sectional detail view as seen along the line 8 8in FIG. 7;

FIG. 9 is a sectional view on line 9 9 in FIG. 8; and

FIG. 10 is a diagrammatic electrical control circuit which may be usedwith the apparatus of this invention.

DETAIL DESCRIPTION OF THE INVENTION Referring to FIG. 1 of the drawingsthe apparatus of this invention, designated generally as 15, isillustrated in an assembly relation with a latch mechanism 16 for thedoor 17 of a vehicle body 18 which also includes an instrument panel 19.The latch mechanism 16 includes a usual garnish button 20 for actuatinga shiftable rod and lever arrangement 21 to'pivotally move an operatinglever 22 to door locking and unlocking positions. As shown in FIG. 2 thelever 22 straddles a foot or leg 23 on a pivoted locking lever 24 whichis selectively become apparent the door lock or garnish button 20 may bemanually moved in a normal manner to either a door opening or doorlocking position whenever the apparatus 15 is de-activated. Conversely,regardless of the manually moved position of the door lock button 20,the apparatus 15, on being activated, immediately takes over to move thebutton 20 from such manually moved position to the other positiontherefor.

The apparatus 15 (FIGS. 3 and 4) includes a mounting bracket 28 of aright angle shape having an upright leg 29 secured to a door framemember 30 as by a bolt 31 and a horizontal leg 32 of a circular shape-inplan view provided with an upwardly projected peripheral wall 33. Areversible electric motor 34 attached to the underside of the horizontalleg 32 has a drive shaft one end section 35 of which extends upwardlythrough a central opening 36'formed in the horizontal leg 32. Mountedabout the shaft end section 35 and in splined driven engagementtherewith, as indicated at 37, is a tubular sleeve 38. As shown in FIG.4, the sleeve 38 projects upwardly from and in coaxial alignment withthe shaft end section 35 so as to form a guide bearing for the lower end39 of an actuator member or rod 40.

Adjacent its upper end (FIGS. 6 and 7) the sleeve 38 carries a pair ofradially projected diametrically opposite pivot pins 41 for pivotallysupporting a pair of centrifugally actuated weight members 42. Eachweight member 42 has a body section 43 of a semicircular shape intransverse cross section integrally formed with an upstanding necksection 44 that is also of a semicircular shape in transverse crosssection. Each neck section 44 is internally threaded so as to form ahalf nut member.

At the junction of a neck section 44 and with the body section 43 eachweight member 42 has a pair of transversely opposite laterally extendedarms 46 formed at their. free ends with openings 47. The arms 46 aresupported at the openings 47 on the pivot pins 41 (FIG. 9). When thesleeve member 38 is not being rotated the weight members 42 aresuspended from the pivot pins 41 with the body sections 43 hungvertically downwardly in a concentrically spaced relation about theguide sleeve 38 and the neck sections 44 projected upwardly in adiverged relation from opposite the sides of the actuator member 40, allas shown in dotted lines in FIG. 5.

On rotation of the tubular guide sleeve 38 the body sections 43, inresponse to centrifugal action, are swung outwardly into a downwardlydiverged relation from the pivot pins 41, (FIGS. 5 and 8) whereby theneck sections 44 are moved inwardly toward each other into a matingrelation to form a split nut that is extended about and in coaxialalignment with the actuator rod 40. As illustrated in FIGS. 4 and 5, theactuator rod 40 has a central section 48 that is guidably supported forreciprocal movement within a tubular bearing 49 projected upwardly fromand integrally formed with a housing or casing 51 for the weight members42 and sleeve 38. The housing 51 is of a generally frustoconical shape,with its lower end positioned about and in a snap-lock engagement, asindicated at 52, with the peripheral wall 33 of the mounting bracket 28.

Intermediate the central section 48 and lower section 39 of the actuatorrod 40, the rod is formed with a shaft section 53 which is separatedfrom the lower section 39 and central section 48 by reduced rod portions54 and 55, respectively. Stated otherwise, the shaft section 53 isdefined by the reduced rod sections 54 and 55, to provide a shaftsection of a predetermined length relative to the reciprocal path oftravel of the door button 20 from a door locking position to a dooropening position.

Intermediate the upper end section 56 and the central section 48 of theactuator rod 40 is what will be referred to as an abutment section 57which is separated fromthe central section 48 and upper section 56 byreduced rod portions 58 and 59, respectively. Referring to FIGS. 4 and5, it is seen that the central section 48 is extendible outwardly orupwardly from the tubular bearing 49 so that the portion of the rod 40located between the upper section 56 and the central section 48 isalways exposed above the bearing member 49. This exposed portion of therod 40 forms part of a conversion unit, indicated generally as 61, thatprovides for a manual or electrical operation of the apparatus at thewill of the operator.

This conversion unit 61 includes additionally a tubular housing orconnecting member 62 that has a lower section 63, an intermediatesection 64 and an upper section 66 of progressively reduced diameters toform shoulders 67 and 68 at the junction of the center section 64 withthe lower section 63 and upper section 66, respectively. The lowersection 63 is movable in a telescopic relation about and relative to thetubular member 49 and is formed at its bottom end with a pair ofinwardly projected diametrically opposite lugs or keys 69 that areguidably movable within corresponding grooves or ways 71 extendedlongitudinally of and formed in the outer peripheral surface of thebearing member 49.

Mounted about the rod abutment section 57 is a coil spring 72 that iscompressible between washers 73 and 74 movably mounted about the reducedrod sections 58 and 59 and engageable with the shoulders 67 and 68, allrespectively. The spring 72 and the abutment section 57 are thus alwayslocated within the center section 64 of the tubular connecting member62. The upper end of the top section 66 of the connecting member 62 isinternally threaded, as indicated at 76, for threaded engagement with aconnecting link 77 (FIG. 2) that is operatively connected with the doorlock button 2t and the rod and lever arrangement 21 for actuating thelatch mechanism 16.

In the use of the apparatus 15, let it be assumed that the door lockbutton is in its door opening position and the motor 34 de-energized asillustrated in FIG. 5 so that the weight members 42 are in their dottedline positions. The actuator rod 40 is thus in its uppermost movedposition with the connecting member 62 extended from the bearing member49. It will also be seen that the washer 74 has been moved intoengagement with the shoulder 68 by the abutment rod section 57 and thatthe washer 73 has been moved out of engagement with the shoulder 67 bythe central section 48. The spring 72 thus exerts a slight downwardyieldable pressure tending to move the actuator rod 40 downwardly to aposition wherein the lower end of the threaded shaft section 53 can beengaged by the nut half portions 44 on movement inwardly toward eachother. Thus, on energization of the motor 34 to move the button 20downwardly to a door locking position, the shaft section 53 isimmediately engaged by the rotating nut portions 44 to move the rod 40downwardly to its position shown in FIG. 4. The weight members 42 andsleeve 38 thusconstitute a centrifugally actuated clutch unit forconnecting the actuator rod 40 in a driven relation with the motor 34.

During the initial downward movement of the actuator rod 40, the actionof the spring 72 to move the rod 40 downwardly is retained until thewasher 78 abuts the shoulder 67. With the washers 73 and 74 against theshoulders .67 and 68, respectively, the spring 72 is in its most fullyextended and neutral position. In such neutral position, the spring iswithout any action on the actuator rod 40. This non-action of the spring72 takes place by virtue of the relative slidable movement of thewashers 73 and 74 on the reduced rod sections 58 and 59, respectively.On a continued downward movement of the actuator rod 40 the lower faceof the abutment section 57 moves into engagement with the washer 73,which as stated above is in abutting engagement with the shoulder 67.When this engagement takes place the rod 40 and the tubular housing 51are moved downwardly as a unit. Concurrently with the abutment of thesection 57 with the washer 73 to move the housing 51 downwardly theupper face of the abutment section 57 is moved away from the washer 74by the engagement of the washer 74 with the downwardly moving upper rodsection 56 as seen in FIG. 4.

As a result of this engagement of the washer 74 by the upper rod section56 the spring 72 acts to apply a yieldable pressure upwardly on theactuator rod 40. Thus when the split nut that is comprised of the nuthalf portions 44 overruns the upper end of the threaded shaft section53, such upper end is maintained in riding engagement against the splitnut whereby to eliminate any lost motion or rattling between the splitnut and the shaft 53 while the motor 34 is running. On shutting off ofthe motor 34 the weight members 42 are moved by the action of gravity totheir suspended positions from the pivot pins 41 and out of engagementwith the rod 40 which is held in its door lock position of FIG. 4 by thetoggle action of the spring 25 in the door latching mechanism 16.

To unlock the vehicle door 17 the motor 34 is operated to move the splitnut portions 44 into engagement with the lower end of the shaft section53. By virtue of the reversed rotation of the rod 40 relative to itsrotation for locking the vehicle door, rod 40 is linearly moved upwardlyto its position of FIG. 5. During this upward movement of the actuatorrod 40 the casing 51 is moved upwardly when the washer 74 and the upperface of the abutment section 57 are moved against the shoulder 68.

Since the action of the spring 72, during the upward movement of theactuator rod 40, is reversed relative to its action when the rod 40 isbeing moved downwardly, the lower end of the shaft section 53 iscontinuously biased into riding engagement with the split nut on theweight members 42 to prevent any rattling therebetween while the motor34 is running. Also, it will be noted that on stopping of the motor 34and the moving of the weight members 42 by gravity to their suspendedpositions from the pivot pins 41 that the actuator rod will be held in avehicle door unlocking position by the toggle action of the spring 25 inthe latch mechanism 16.

If the door lock button 20 is to be manually moved to a door lockingposition, from its unlocking position shown in FIG. 5, such is done bymerely depressing the button 20 in the usual manner. On depression ofthe button 20 the connecting member 62 is moved downwardly to in turnmove the actuator rod 40 from its position shown in FIG. 5 to theposition therefor shown in FIG. 4 wherein the split nut portions 44 arelocated adjacent the upper end of the threaded shaft section 53 andopposite the reduced rod section 55. Thus, the relative positions of theapparatus 15 following this manual movement is in all respects the sameas shown in FIG. 4 when the like movement of the rod 40 was accomplishedby operation of the motor 34.

Similarly, when the actuator rod 40 is in its door locking positionshown in FIG. 4, it is manually movable independently of the motor 34 toa door unlocking position by pulling upwardly on the door lock button 20in a usual manner. During this manual operation of the button 20 toeither lock or release the vehicle door 17, it will be seen that thehalf nut portions 44 are always located opposite one or the other of thereduced rod sections 54 and 55 so as to be engageable with the rod shaftsection 53 to electrically operate the rod 40 in a reversed directionrelative to the last direction of movement thereof.

FIG. illustrates diagrammatically an electrical control system forsimultaneously operating the motors 34 when an apparatus is associatedwith a latch mechanism 16 on each of the four doors of a vehicle body.The motors 34 are connected in parallel between the leads 78 and 79 of ausual vehicle battery 81. The lead 79 is connected to a three-way switch82 that may be carried on the instrument panel 19. A first feed line 83from the switch terminal 84 is connected to one side of the windings(not shown) of the motors 34 to rotate the motors in a first direction.As is usual a second feed line 86 from the switch terminal 87 connectsthe opposite side of the motor windings to lead line 78 to reverse thecurrent flow through the windings to provide for a reversed rotation ofthe motors 34. The switch actuator 88 is shown in FIG. 10 in its offposition.

I claim:

1. Apparatus for obtaining controlled rectilinear movement comprising:

a. a reversible rotary driving member,

b. a driven member,

c. means supporting said driven member for reversible movement axiallyof said driving member,

d. an intermediate centrifugally actuated member,

e. means supporting said centrifugally actuated member on said drivingmember for pivoted movement about an axis extended diametrically of saiddriving member,

f. coacting portions on said intermediate member and said driven memberforming a nut and a screw having ends for releasably connecting saiddriving member with said driven member when said driving member isrotated, and

g. means for yieldably maintaining the nut portion of said driven memberengageable with one or the other of the ends of the screw after the nutportion has overrun the screw portion.

2. The apparatus according to claim 1 including:

a. means interconnecting said yieldable means with said driven member toprovide for a delayed concurrent movement of said yieldable means withthe driven member in either direction of movement thereof,

b. said driven member, when the centrifugally activated member isdisconnected therefrom, being manually movable in reversed directions.

3. An apparatus for providing a controlled rectilinear movement of arotatably driven actuator member comprising:

a. a support member,

b. a reversible electric motor mounted on said support member having adrive shaft,

c. a sleeve member coaxial with and secured to said drive shaft forrotation therewith,

d. a pair of pivoted centrifugally actuated arm members positioned atopposite sides of said sleeve member,

e. means pivotally supporting said arm members on said sleeve member forinward pivotal movement of one of the end sections thereof toward eachother when the sleeve member is rotated, each of said end sections beingformed with a half nut portion, said half nut portions relativelyarranged to form a split nut when said end sections are in the inwardlymoved positions therefor,

f. said actuator member comprised of a cylindrical rod having a firstsection guidably supported within said sleeve member for axial movementrelative thereto, and a second section,

g. said first section having a threaded portion of a length defined byrod portions of reduced diameter at opposite ends thereof, said threadedportion engageable with said split nut when said sleeve member isrotated, and

h. means mounted on said supporting member and engageable with saidsecond section of the rod to yieldably urge the rod in a lineardirection corresponding to a position of said split nut at one or theother of said rod portions of reduced diameter, whereby one or the otherof the termini of said threaded portion is yieldably held against saidsplit nut after rotation of said threaded portion out of threadedengagement with the split nut.

4. An apparatus for providing a controlled rectilinear movement of arotatably driven actuator member comprising:

a. a frame structure,

b. a reversible electric motor mounted on said frame structure having adrive shaft,

c. centrifugally actuated clutch means secured to said drive shaft forrotation therewith including coacting nut portions,

(I. said actuator member comprised of a rod having a first section and asecond section,

e. means on said frame structure supporting said second section forrectilinear movement,

f. said first section having a threaded portion engageable with said nutportions, said nut portions movable into engagement with said threadedportion when said drive shaft is rotated, said first section formed witha portion of reduced diameter at each end of said threaded portionwhereby rectilinear movement of said rod is terminated in eitherdirection of movement thereof on disengagement of said nut portions fromsaid threaded portion when said nut portions are opposite one or theother of said reduced diameter rod portions, and

f. means on said frame structure for yieldably urging said rod in adirection opposite to the direction of rectilinear movement thereof toretain the disengaged nut portions in contact with the adjacent terminalend of said threaded portion, whereby on a reversed rotation of said nutportions, said threaded portion is engageable with the nut portions torectilinearly move said rod in a reversed direction relative to the lastdirection of movement thereof.

5. The apparatus according to claim 4 wherein said yieldable meansincludes:

a. a cylindrical sleeve member positioned about the second section ofsaid rod,

b. means supporting the cylindrical sleeve on said frame structure forrelative movement axially of said rod,

c. a coil spring within said sleeve member mounted about said rod forextensible movement axially of said rod between predetermined stopportions on said rod, and

d. means on said cylindrical sleeve member for compressing said springrelative to said stop portions in response to movement of said rod ineither direction.

6. Apparatus for obtaining controlled rectilinear movement comprising: areversible rotary driving member, a driven member, means supporting saiddriven member for reversible movement axially of said driving member, anintermediate centrifugally actuated member, means supporting saidcentrifugally actuated member on said driving member for pivotedmovement about an axis extended diametrically of said driving member,and coacting portions on said intermediate member and said driven memberforming a nut and screw system for releasably connecting said drivingmember with said driven member when said driving member is rotated, saiddriven member including spaced sections of reduced cross section.

7. A linear actuator comprising: an axially movable threaded member, arotatable member, and centrifugally actuated means including threads andmovably supported on said rotatable member for generally radial movementbetween a non-rotating at rest position with said threads disengagedfrom said threaded member and a rotating active position with saidthreads engaging said threaded member to move said threaded memberaxially, said threaded member including a section of reduced crosssection at each end of the threaded section thereof.

8. An actuator as set forth in claim 7 including means supporting saidthreaded member for axial movement by said centrifugally actuated meansand by other means when said centrifugally actuated means is in saidnon-rotating at rest position.

9. An actuator as set forth in claim 7 wherein said centrifugallyactuated means includes a pair of arms pivotally attached to saidrotatable member.

10. An actuator as set forth in claim 9 wherein each of said armsincludes a weight portion below the pivotal attachment thereof to saidrotatable member and a half nut portion above said pivotal attachment,said threads being in said nut portions of said arms.

1. Apparatus for obtaining controlled rectilinear movement comprising:a. a reversible rotary driving member, b. a driven member, c. meanssupporting said driven member for reversible movement axially of saiddriving member, d. an intermediate centrifugally actuated member, e.means supporting said centrifugally actuated member on said drivingmember for pivoted movement about an axis extended diametrically of saiddriving member, f. coacting portions on said intermediate member andsaid driven member forming a nut and a screw having ends for releasablyconnecting said driving member with said driven member when said drivingmember is rotated, and g. means for yieldably maintaining the nutportion of said driven member engageable with one or the other of theends of the screw after the nut portion has overrun the screw portion.2. The apparatus according to claim 1 including: a. meansinterconnecting said yieldable means with said driven member to providefor a delayed concurrent movement of said yieldable means with thedriven member in either direction of movement thereof, b. said drivenmember, when the centrifugally activated member is disconnectedtherefrom, being manually movable in reversed directions.
 3. Anapparatus for providing a controlled rectilinear movement of a rotatablydriven actuator member comprising: a. a support member, b. a reversibleelectric motor mounted on said support member having a drive shaft, c. asleeve member coaxial with and secured to said drive shaft for rotationtherewith, d. a pair of pivoted centrifugally actuated arm memberspositioned at opposite sides of said sleeve member, e. means pivotallysupporting said arm members on said sleeve member for inward pivotalmovement of one of the end sections thereof toward each other when thesleeve member is rotated, each of said end sections being formed with ahalf nut portion, said half nut portions relatively arranged to form asplit nut when said end sections are in the inwardly moved positionstherefor, f. said actuator member comprised of a cylindrical rod havinga first section guidably supported within said sleeve member for axialmovement relative thereto, and a second section, g. said first sectionhaving a threaded portion of a length defined by rod portions of reduceddiameter at opposite ends thereof, said threaded portion engageable withsaid split nut when said sleeve member is rotated, and h. means mountedon said supporting member and engageable with said second section of therod to yieldably urge the rod in a linear direction corresponding to aposition of said split nut at one or the other of said rod portions ofreduced diameter, whereby one or the other of the termini of saidthreaded portion is yieldably held against said split nut after rotationof said threaded portion out of threaded engagement with the split nut.4. An apparatus for providing a controlled rectilinear movement of arotatably driven actuator member comprising: a. a frame structure, b. areversible electric motor mounted on said frame structure having a driveshaft, c. centrifugally actuated clutch means secured to said driveshaft for rotation therewith including coacting nut portions, d. saidactuator member comprised of a rod having a first section and a secondsection, e. means on said frame structure supporting said second sectionfor rectilinear movement, f. said first section having a threadedportion engageable with said nut portions, said nut portions movableinto engagement with said threaded portion when said drive shaft isrotated, said first section formed with a portion of reduced diameter ateach end of said threaded portion whereby rectilinear movement of saidrod is terminated in either direction of movement thereof ondisengagement of said nut portions from said threaded portion when saidnut portions are opposite one or the other of said reduced diameter rodportions, and f. means on said frame structure for yieldably urging saidrod in a direction opposite to the direction of rectilinear movementthereof to retain the disengaged nut portions in contact with theadjacent terminal end of said threaded portion, whereby on a reversedrotation of said nut portions, said threaded portion is engageable withthe nut portions to rectilinearly move said rod in a reversed directionrelative to the last direction of movement thereof.
 5. The apparatusaccording to claim 4 wherein said yieldable means includes: a. acylindrical sleeve member positioned about the second section of saidrod, b. means supporting the cylindrical sleeve on said frame structurefor relative movement axially of said rod, c. a coil spring within saidsleeve member mounted about said rod for extensible movement axially ofsaid rod between predetermined stop portions on said rod, and d. meanson said cylindrical sleeve member for compressing said spring relativeto said stop portions in response to movement of said rod in eitherdirection.
 6. Apparatus for obtaining controlled rectilinear movementcomprising: a reversible rotary driving member, a driven member, meanssupporting said driven member for reversible movement axially of saiddriving member, an intermediate centrifugally actuated member, meanssupporting said centrifugally actuated member on said driving member forpivoted movement about an axis extended diametrically of said drivingmember, and coacting portions on said intermediate member and saiddriven member forming a nut and screw system for releasably connectingsaid driving member with said driven member when said driving member isrotated, said driven member including spaced sections of reduced crosssection.
 7. A linear actuator comprising: an axially movable threadedmember, a rotatable member, and centrifugally actuated means includingthreads and movably supported on said rotatable member for generallyradial movement between a non-rotating at rest position with saidthreads disengaged from said threaded member and a rotating activeposition with said threads engaging said threaded member to move saidthreaded member axially, said threaded member including a section ofreduced cross section at each end of the threaded section thereof.
 8. Anactuator as set forth in claim 7 including means supporting saidthreaded member for axial movement by said centrifugally actuated meansand by other means when said centrifugally actuated means is in saidnon-rotating at rest position.
 9. An actuator as set forth in claim 7wherein said centrifugally actuated means includes a pair of armspivotally attached to said rotatable member.
 10. An actuator as setforth in claim 9 wherein each of said arms includes a weight portionbelow the pivotal attachment thereof to said rotatable member and a halfnut portion above said pivotal attachment, said threads being in saidnut portions of said arms.